Apparatus for forming a multiple tube panel



Nov. 20, 1962 E. w. ALLARDT APPARATUS FOR FORMING A MULTIPLE TUBE PANEL6 Sheets-Sheet 1 Filed NOV. 5, 1956 ATTORNEY E. w. ALLARDT Nov. 20,1962' APPARATUS FOR FORMING A MULTIPLE TUBE PANEL 6 Sheets-Sheet 2 FiledNOV. 5, 1956 F l G. 2 INVENTOR [2775f WJW/Qrdi ATTORNEY Nov. 20, 1962 E.w. ALLARDT APPARATUS FOR FORMING A MULTIPLE TUBE PANEL 6 Sheets-Sheet 3Filed Nov. 5, 1956 W L/ m J m 3 5 r M H 4 q .L f L r v @E 5 1'1 E w, M 0a E Q Q FIG.3

ATTORNEY 1962 E. w. ALLARDT 3,065,329

APPARATUS FOR FORMING A MULTIPLE TUBE PANEL Filed Nov. 5, 1956 6Sheets-Sheet 4 INVENTOR Z 2752 Wa /Yard ATTORNEY Nov. 20, 1962 E. w.ALLARDT 3,065,329

APPARATUS FOR FORMING A MULTIPLE TUBE PANEL Filed NOV. 5, 1956 6Sheets-Sheet 5 ATTORNEY Nov. 20, 1962 E. w. ALLARDT APPARATUS FORFORMING A MULTIPLE TUBE PANEL United States Patent Ofitice 3,065,329APPARATUS FGR FGRMING A MULTIPLE TUBE IANEL Ernst W. Allardt, Alliance,@hio, assignor to The Babcock & Wilcox Company, New York, N.Y., acorporation of New Jersey Filed Nov. 5, 1956, er. No. 620,424 5 Claims.(Cl. 219-402) This invention relates to tube panels or walls, formingcomponents of a heat exchanger, and to a novel method of making suchpanels or walls. More particularly the invention is directed to animpervious or pressure-tight tube panel or wall comprising a pluralityof metal tubes held in relatively closely spaced and substantiallyparallel relation by interposed web or spacer strips electric resistancewelded along opposite longitudinal edges to adjacent tubes, and toapparatus for, and a method of, forming such panels or walls by electricresistance welding.

Many vapor generating installations have furnaces, or other portionssubjected to high temperature gases, enclosed by water walls formed ofgenerally upright tubes supplied with fluid for vapor generation byabsorption of heat from the gases. These tubes are relatively closelyspaced and frequently closely studded to provide a substantiallycontinuous heat absorbing surface. Interspaces are packed withrefractory to provide a substantially impervious enclosure. 1

However, it is necessary, in order to provide a leaktight andpressure-tight enclosure, to enclose these walls in an outer metalcasing or skin secured to the walls by bolting, spot welding, or thelike, and this casing represents a substantial expense in the cost ofthe vapor generator. This expense could be eliminated by a leak-tightand pressure-tight water wall construction.

As a proposed solution, it has been suggested that tube panels or wallsbe formed by welding the tubes to each other, either directly or byconnecting or spacer strips welded between adjacent tubes, and suchpanels have actually been formed by fusion welding techniques.

However, fusion welding, particularly of the arc welding type, ischaracterized by relatively high temperatures sufiicient to meltsubstantial portions of the metal at the joints. These high temperaturesresult in relatively large heat affected zones in the welded members,with correspondingly increased distortion in the parts as-welded.Relatively extensive and expensive post-weld heat treat ment is requiredto effectively reduce or eliminate the locked-in stresses. In theparticular example of fusion weld uniting closely spaced tubes by aspacer strip or web, extensive working of the welded structure isgenerally necessary to re-shape the same to a fiat or planar state withthe interconnected tubes being rectilinear.

Fusion welding techniques also are not as readily adapted to productionline operations as are other weld ing techniques because of their slowspeed of operation. To overcome this handicap, a multiplicity of weldingheads have to be employed, which greatly adds to complexity of theoperation.

In accordance with the present invention, a tube panel or wall isprovided comprising a plurality of closely laterally spaced, andrelatively elongated metal tubes integrally united into a leak-tight andpressure-tight structure by interposed metal webs or spacer stripselectrical resistance welded along opposite longitudinal edges toadjacent tubes.

The apparatus for forming the tube panels or walls comprises two pairsof co-axial rotary electric resistance Welding electrodes, theelectrodes of each pair being mounted in juxtaposed electricallyinsulated relation and connected to opposite polarity terminals of asource of 3,065,329 Patented Nov. 20, 1962 welding potential with eachpair of electrodes preferably being connected to opposite terminals of adifferent transformer secondary winding. The two pairs of electrodes arearranged in vertically adjacent relation with correspondingly locatedelectrodes of the two pairs being in substantial alignment verticallyand laterally and at the same relative polarity.

Each electrode has an outwardly concave curved tube engaging peripheralsurface, the tube engaging surfaces of laterally adjacent coaxialelectrodes thus diverging toward the electrode axis. Thereby, theelectrodes of the upper pair engage the upper inner quadrants, and thoseof the lower pair the lower inner quadrants, of a pair of tubes fed inlaterally spaced relation between the two pairs of electrodes. However,the minimum peripheral spacing of vertically aligned electrodes is inexcess of the thickness of a metal web or strip fed between the tubes,so that the electrodes contact only the tubes and not the strip.

Thereby, the resistance welding current flows from one electrode of eachpair into one tube, through or across the strip, into the other tube andout through the other electrode of each pair. By using two pairs ofelectrodes, one above the strip and the other below the strip, anddividing the total welding current substantially equally between the twopairs, the welding current is distributed substantially uniformlythroughout the depth of the strip, resulting in uniformly goodresistance welds across the entire vertical extent of the contactingsurfaces.

A guiding means, preferably in the form of a roller conveyor or thelike, is provided to feed pairs of tubes to guiding rollers or the likein advance of the electrodes. Other guiding means extend substantiallyto the common axial plane of the two pairs of electrodes to guide themetal web or strip between the tubes, preferably at or adjacent thecommon diametrical plane thereof. The tube guiding rollers are soarranged as to feed one tube rectilinearly to the electrodes and theother tube in converging relation to such one tube so that both tubescontact the strip edges substantially only when they engage theelectrodes. Thereby, a resistance welding circuit is completed only asthe tubes and strip enter the welder.

Squeeze roll means are provided to forcibly press the tubes against thestrip edges as the resistance Welding current flows through the assemblyof tubes and strip. The squeeze roll means include a single squeeze rollmounted on a substantially vertical axis and engaging the outerperiphery of one tube, and a pair of squeeze rolls rotatable in planesdiverging at substantially 45 to the horizontal and vertical andengaging the outer periphery of the other tube. The single squeeze rollhas a concave periphery conformingly engaging substantially the entireouter periphery of the one tube between the upper and lower electrodes.One of the pair of squeeze rolls engages the upper outer quadrant of theother tube and the other of the pair of squeeze rolls engages the lowerouter quadrant thereof. However, the minimum spacing of the peripheriesof the paired squeeze rolls is at least equal to the thickness of theweb or strip, for clearing the latter as additional tubes and strips areelectric resistance welded to the initially joined tube and stripassembly.

The joined tubes and strip leaving through a set of straightening andpull laterally shiftable roller conveyor. tube and strip assemblylaterally to return to the first conveyor. The first conveyor is alsolaterally shiftable to re-align one tube of the assembly with the welderfor passage therethrough with an added strip and tube to extend thepanel laterally. The previously welded strip passes between the pairedsqueeze rolls the welder pass out rolls onto a The latter shifts theclear the welder for 3 with the other tube joined thereto passingoutside these squeeze rolls.

In practicing the method of the invention, a first pair of tubes arejoined to a strip by electric resistance welding by the describedapparatus. This first pair of joined tubes is then returned tosubstantially its starting position, but offset laterally thereof by theamount of the inter-tube spacing. The joined first pair of tubes, asecand strip, and a third tube are then fed to the welder, with thethird tube, the strip, and one of the first pair of tubes beingresistance welded to each other, the other tube of the first pairpassing outside the welder and the initial web or strip clearing thespaced paired squeeze rolls. The sequence is then repeated until a panelof the desired width has been formed. Preferably, to avoid distortion inthe plane of the panel, successive tubes are added to alternate sides ofthe panel, thereby equalizing any distortion, in the plane of the panel,as might occur if all the tubes were added successively to the same sideof the panel. Such alternate side extension may be effected, forexample, by turning the panel over between successive passes through thewelder.

For an understanding of the invention principles, reference is made tothe following description of a typical embodiment thereof as illustratedin the accompanying drawing. In the drawing:

FIG. 1 is a side elevation view of an electric resistance welderembodying the invention;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a plan view of the welder;

FIG. 4 is a front elevation view, partly in section, of the adjustablemounting of one squeeze roll;

FIG. 5 is a plan view of tube panel or wall forming apparatusincorporating the welder;

FIG. 6 is an enlargement of a portion of FIG. 5; and

FIG. 7 is a front elevation view of the apparatus.

Referring to FIGS. 1, 2 and 3, the electric resistance welder 10 ismounted in a support frame including columns 11 and a top cross member12 interconnecting the columns. The columns have facing inwardextensions 13 forming vertical guides for slides 14, 14 in which aremounted rotary welding transformers 15, 15 which may be of the typeillustrated and described in US. Patent 2,666,121, issued January 12,1954, to E. W. Allardt. As described in said patent, each rotary weldingtransformer includes a single turn secondary winding comprisingconcentric inner and outer cylindrical or tubular members telescopedover each other with dielectric material therebetween. These members areelectrically connected at one end and, at their outer end, conjointlyform tapered seats for a pair of rotary welding electrodes securedtogether as a unit with a disk 25, of dielectric material interposedtherebetween. These electrodes are described more fully hereinafter.

Transformers 15, 15 may be rotated by means of electric motors 16, 16'mounted on columns 11 and having drive sprockets 17, 17' connected bychains 18, 18' to ring sprockets 19, 19 on the transformers. Verticaladjustment of the transformers 15, 15 is effected by motors 21, 21driving gear reducers 22, 22' having rotatable nuts (not shown) threadedon screw shafts 23, 23' secured to slides 14, 14. Motor 21 is mounted ontop support 12 and motor 21 is mounted in a pit or recess 24.

The pairs of electrodes 20A, 20B and 26C, 20D are reversely disposed ascompared to the usual electrode disposition used in forming the seam inERW tubing.

Thus, while each electrode has an outwardly concave peripheral orwork-contacting surface 26, the pairs of electrodes are so disposed thattheir surfaces 26 diverge from each other toward the electrode ortransformer axis. The axes of the two transformers 15, 15 are in acommon vertical plane, and the upper and lower pairs of electrodes arein vertical alignment laterally of the welder 10.

Each pair of electrodes forms the terminals of the secondary winding ofits associated transformer, and the relative polarities of the fourelectrodes are such that electrodes 20A and 200 are at the samepolarity, and electrodes 29B and 20D are at the opposite polarities. Inthe absence of unforseen fluctuations in the power supply, electrodes20A and 20B are at the same potential as electrodes 20C and 20D,respectively. Thus, under normal conditions of steady power supply,there is no current circulating between the two transformers 15 and 15'.The contact surfaces 26 of the electrodes are dressed by tools 27, 27'adjustably mounted in brackets 28, 23 on columns 11.

The electrodes 20A, 20B are arranged to engage the upper innerquadrants'of a pair of metal tubes 30 fed through the welder 10 in amanner to be described, and pressed firmly against opposite longitudinaledges of a metal spacer strip 31 while the tubes are engaged by thewelding electrodes. The lower electrodes 20C, 20D engage the lower innerquadrants of the tubes. The surfaces 26 extend through substantially 90of arc.

The minimum spacing of the peripheries of electrodes 20A and 2013 fromthe adjacent peripheries of electrodes 20C and 20D, respectively, is atleast slightly in excess of the thickness of webs 31. Thus, none of theelectrodes contact a strip or web- 31. Consequently, the electricresistance welding currents flow over two parallel paths as follows: (1)electrode 20A, left tube 30, strip 31, right tube 30, electrode 20B; and(2.) electrode 20C, left tube 30, strip 31, right tube 30, electrode20D.

By providing two current flow paths, one adjacent the upper sideof strip30 and the other adjacent the lower side thereof, the current isdistributed substantially uniformly of the vertical extent of thelongitudinal edges of strip 31, thus resulting in a uniform resistancewelding of the entire surfaces of the strip edges to the tubes 30. Thisis in contrast to the case where only a single pair of electrodes isused. In this case, the current flow is concentrated more to the upper(or lower) side of the strip with the result that the best weld isobtained between the strip and tube surfaces nearest the electrodes,with the weld decreasing in quality away from the electrodes. The use oftwo pairs of electrodes has the further advantage that the current isdivided between the two sets of electrodes. Consequently, for a givenrequired total current, the current density at the contact surfaces 26is reduced substantially 50 percent as compared to the current densityif only a single pair of electrodes were used.

Pressing of the tubes into firm contact with thelongitudinal edges ofstrip 31 is effected by conjointly adjustable squeeze roll meansincluding a single squeeze roll 35, engaging the outer surface of theleft hand tube (FIG. 1) over substantially one-half of itscircumferential extent, and a pair of squeeze rolls 40, 40* engaging theright hand tube3tl (FIG. 1). Roll 40 engages this latter tube over mostof the upper outer quadrant and roll 40 engages it over most of thelower outer quadrant, the peripheries of rolls 40 and 40, at theirclosest approach, being separated by at least the thickness of webs 31.

Squeeze roll is rotatably mounted on a vertical axis in a forked support32 which is adjustable laterally of tubes 30 in a slide 33 in turnmounted for longitudinal adjustment in a support 34 extending betweenextensions 13 of columns 11. Squeeze roll is mounted, for rotation in aplane extending at substantially to the horizontal and vertical, in adepending bracket 36 which is slidably mounted, for adjustment laterallyrelative to tubes 30, in a slide 37 adjustable longitudinally of a crossmember 38 secured at each end to slides 41 adjustable vertically inguides 42 along the front surfaces of corners 11.

Squeeze roll 35 is substantially fixed vertically of welder 10. Conjointvertical adjustment of squeeze rolls 40 and 40 is effected by verticalshafts 43, rotatably mounted in thrust bearings in brackets 44 securedto columns 11 and fixed against vertical movement by the thrustbearrolls 86, 86

ings. The upper and lower ends of shafts 43 are threadedly engaged inslides 41, and the shafts are provided with sprockets 46 interconnectedby a chain or the like 47. The upper end of one shaft 43 is squared, asat 45, for application of a suitable crank or the like for conjointlyrotating both shafts 43. The upper and lower ends of each shaft arethreaded in opposite directions so that, upon rotation of the shafts,squeeze rolls 40 and 40 are moved closer together or farther apart toaccommodate different sized tubes. For this purpose, the squeeze rolls35, 40 and 40" are made readily removable for exchange with othersqueeze rolls having peripheral tube engaging surfaces corresponding todifferent sized tubes 30.

The lateral spacing of squeeze roll 35 from squeeze rolls 40 and 40' iseffected in the following manner. A shaft 51 has an end threadedlyengaged in support 32 for squeeze roll 35, the outer end of shaft 51carrying a bevel gear 52 engaged with a bevel gear 53 on a shaft 54extending longitudinally of the welder. Shafts 56, 56 are threaded intosupports 36, 36' and fixed against axial movement relative to supports37, 37. The outer ends of shafts 56, 56' carry bevel gears 57, 57engaged respectively with bevel gears 58, 5% on shafts 50 and 50interconnected for conjoint operation by an endless chain extending oversprockets secured to the shafts, this interconnection being omitted tosimplify the drawing. The other end of shaft 50 carries a sprocket 59connected by a chain 55 to a sprocket 61 secured, for rotation with asprocket 62, on a shaft 69. A chain 63 connects sprocket .62 to asprocket 64 on the outer end of shaft 54. By the described arrangement,when either shaft is rotated, the squeeze rolls are moved laterally toincrease or decrease the effective spacing therebetween.

Provision is also made for adjustment of the squeeze rollslongitudinally of the welder. A shaft 65 is threaded into support 32 andcarries a sprocket 66 connected by a chain 67 to a sprocket 68 on ashaft 69'. Shafts 70 and 70 are threaded into slides 37 and 37',respectively, and are interconnected by chain and sprocket connectionsto each other. The outer end of shaft 69 carries a sprocket 71 connectedby a chain to a sprocket 72 fixed to rotate with. a sprocket 73 on ashaft 75. A chain connects sprocket 73 to a sprocket 74 on the outer endof shaft 70.

When either shaft 69 or shaft 70 is rotated, the three squeeze rolls aremoved in one direction or the other longitudinally of welder 1G. Thedescribed adjustments provide for accurate setting of the distancebetween the squeeze rolls, for accurate adjustment of the squeeze rollslongitudinally of the welder relative to the common axial plane of theelectrodes 20, and for ready adjustment of the vertical spacing betweensqueeze rolls 4t and 40 for accommodation of tubes of differentdiameter.

Referring to FIGS. 5, 6 and 7, the tubes are fed to welder by reversiblehigh speed, flat roller conveyor 80. This conveyor feeds the tubes to aguide roll stand 84 having, for example, three sets of guide rolls eachcomprising an upper roll 85 and a lower roll 85. These rolls areinterchangeable and have concave peripheral surfaces curved to fit thesurfaces of the particular size of tubes being welded into a panel. Itwill be noted that each roll has three axially spaced tube engagingsurfaces 81, 82 and 83, and that surface 81 is spaced a substantiallygreater distance from surface 82 than is surface 83. Surface 82 islongitudinally aligned with the surfaces 26 of electrodes 26B and 26D,whereas surface 81 is substantially offset laterally outwardly fromsurfaces 26 of electrodes 26A and C. The spacing of surfaces 82 and 83is substantially equal to the width of strip 31 when resistance weldedto adjacent tubes 30. The larger spacing of the surfaces 81 and 532permits the strip 31 to be positioned between the tubes on thesesurfaces. The purpose of this arrangement will be set forth in thedescription of the operation of the apparatus.

- From rolls 85, the tubes are fed to a pair of guide each having a pairof concave, tube engaging, peripheral portions 87, 8S spaced axially adistance slightly greater than the width of strip 31. Rolls 86, 86engage the tubes just before the latter enter electrodes 20. The weldedtubes leaving the electrodes are engaged by a closing roll 89 rotatablein a horizontal plane.

The newly joined pair of tubes and the strip therebetween then enter astraightening roll stand 90 comprising a pair of longitudinally spacedupper rolls 91 and a lower roll 92 longitudinally between the upperrolls. Both the upper rolls and the lower roll have axially adjacentpairs of concave, tube-engaging peripheral surfaces 93. Rolls 91 and 92engage only the two tubes which have been passed through the welder, andare relatively adjustable to provide the desired degree ofstraightening. A pull out roll stand 95, comprising several pairs ofupper and lower rolls 94, 94' having three axially adjacent concaveperipheral surfaces 96 to engage the two newly welded tubes and the nextadjacent tube, moves the panel onto a fiat reversible, high speed rollerconveyor 100.

When the trailing end of the panel has emerged from roll stand 95,pusher means 97 are operated to move the panel laterally of conveyor 100to clear welder 10. Conveyor 109 is then activated to move the panel tothe right (FIGS. 5, 6 and 7) onto flat high speed reversible rollerconveyor which returns the panel to conveyor 80 where pushers 98 movethe panel laterally back to its starting position. The sequence of panelmovement may be made automatic by the use of suitably located steps orlimit switches engaged by the panel.

In a preferred sequence of adding tubes to the firstjoined pair of tubesto form the panel, successive tubes are added alternately to oppositesides of the panel. This counteracts or balances any heat engenderedstresses tending to warp the panel parallel to its general plane.Warpage at right angles to the plane of the panel can be easilycorrected by the usual tube straightening techniques as the stiffness ofthe panel in a direction normal to its plane is only a fraction of itsstiffness in a direction parallel to its plane.

In a typical sequence, for example, tubes 30A and 30B, with strip 31A,are passed through welder 10 to electric resistance weld the tubes tothe opposite edges of the strip. In the next pass through welder 10,tube 30C is joined to tube 30A by strip 3113. Before the next pass, thepanel is turned over, side for side, by any suitable means such as anoverhead crane. Tube 30D is then joined to tube 30B by strip 31C. Thepanel is again turned over between passes, and tube 30B is joined totube 36C by strip 31D. The sequence is continued until a panel of thedesired width has been formed. For example, typical panels may be 6 to 8feet wide and 40 to 60 feet long, and may comprise tubes sized from 1inch to 3% inches nominal diameter electric resistance welded togetherby strips or webs /2 inch wide and lIlCll thick. The foregoing examplesare cited merely for exemplary purposes and are in no way limiting.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventionprinciples, it will be understood that the 1nvent1on may be embodiedotherwise without departing from such principles.

What is claimed is:

1. Apparatus for forming an integrated multiple tube panel composed oflaterally spaced relatively elongated metal tubes integrally united by alongitudinal metal web between adjacent tubes electric resistance weldedalong its opposite side edges to the adjacent tubes; said apparatuscomprising, in combination, a first pair of coaxial rotary electrodesmounted in juxtaposed electrically insulated relation and connected toopposite polarity terminals of a source of welding potential; 2. secondpair of coaxial rotary electrodes mounted in juxtaposed electricallyinsulated relation and connected to opposite polarity terminals of asource of welding potential; said two pairs of electrodes being invertically adjacent relation, and correspondingly located electrodes ofthe two pairs being in substantial diametrical alignment vertically andlaterally and being at the same relative polarity; each electrode havinga curved tube engaging peripheral surface and the tube engaging surfacesof the electrodes of each pair diverging from each other in a directiontoward the electrode axis whereby the electrodes of one pair engage theupper inner quadrants throughout substantially 90 degrees of arc, andthe electrodes of the other pair engage the lower inner quadrantsthroughout substantially 90 degrees of arc, of a pair of tubes moved inlaterally spaced relation between the two pairs of electrodes; firstguide means constructed and arranged .to feed a pair of metal tubes'inpredetermined laterally spaced relation to said two pairs of electrodes;second guide means constructed and arranged to guide an elongated metalstrip toward said electrodes between said tubes; squeeze roll meansengaging the outer surfaces of said tubes as the tubes engage theelectrodes to press said tubes firmly against the opposite side edges ofsaid strip for flow of welding current from one electrode of each pairinto one tube, through the strip and through the other tube to the otherelectrode of the associated pair to simultaneously electric resistanceweld both tubes to opposite side edges of said strip; and transfer meansreceiving the joined tubes from said electrodes and constructed andarranged to return the joined tubes to a position in advance of saidguiding means but laterally offset, by the amount of such predeterminedlateral spacing, from the initial position for guiding of one joinedtube and an additional tube, in such predetermined laterally spacedrelation, to said two pairs of electrodes for electric resistance welduniting of another strip and said additional tube to said one joinedtube.

.2. Apparatus for forming an integrated multiple tube panel composed oflaterally spaced relatively elongated metal tubes integrally united by alongitudinal metal web between adjacent tubes electric resistance weldedalong its opposite side edges to the adjacent tubes; said apparatuscomprising, in combination, -a first pair of coaxial rotary electrodesmounted in juxtaposed electrically insulated relation and connected toopposite polarity ter minals of a source of welding potential; a secondpair of coaxial rotary electrodes mounted in juxtaposed electricallyinsulated relation and connected to opposite polarity terminals of asource of welding potential; said two pairs of electrodes being invertically adjacent relation, and correspondingly located electrodes ofthe two pairs being in substantial diametrical alignment vertically andlaterally and being at the same relative polarity; each electrode havinga curved tube engaging peripheral surface and the tube engaging surfacesof the electrodes of each pair diverging from each other in a directiontoward the electrode axis whereby the electrodes of one pair engage theupper inner quadrants throughout substantially 90 degrees of arc, and

the electrodes of the other pair engage the lower inner quadrantsthroughout substantially 90 degrees of arc, of .a pair of tubes moved inlaterally spaced relation between the two pairs of electrodes; firstguide means constructed and arranged to feed a pair of metal tubes inpre-determined laterally spaced relation to said two pairs ofelectrodes; second guide means constructed and arranged to guide anelongated metal strip toward said electrodes between said tubes; squeezeroll means engaging the outer surfaces of said tubes as the tubes engagethe electrodes to press said tubes firmly against the opposite'sideedges of said strip for flow of welding current from one electrode ofeach pair into One tube, through the strip and through the other tube tothe other electrode of the associated pair to simultaneously electricresistance weld both tubes to opposite side edges of said strip; andtransfer means receiving the joined tubes from said el trodes a dconstructed and arranged to shift the joined tubes laterally, and returnthe joined tubes to a position in advance of said guiding means butlaterally offset, by the amount of such predetermined lateral spacing,from the initial position for guiding of one joined tube and anadditional tube, in such predetermined laterally spacedrelation, to saidtwo pairs of electrodes for electric resistance weld uniting of anotherstrip and said additional tube to said one joined tube.

3. Apparatus for forming an integrated multiple tube panel composed oflaterally spaced relatively elongated metal tubes integrally united by alongitudinal metal web between adjacent tubes electric resistance weldedalong its opposite side edges to the adjacent tubes; said apparatuscomprising, in combination, a first pair of coaxial rotary electrodesmounted in juxtaposed electrically insulated relation and connected toopposite polarity terminals of a source of welding potential; a secondpair of coaxial rotary electrodes mounted in juxtaposed electricallyinsulated relation and connected to opposite polarity terminals of asource of welding potential; said two pairs of electrodes being invertically adjacent relation, and correspondingly located electrodes ofthe two pairs being in substantial diametrical alignment vertically andlaterally and being at the same relative polarity; each electrode havinga curved tube engaging peripheral surface and the tube engaging surfacesof the electrodes of each pair diverging fromeach other in a directiontoward the electrode axis whereby the electrodes of one pair engage theupper inner quadrants throughout sub stantially degrees of arc, and theelectrodes of the other pair engage the lower inner quadrants throughoutsubstantially 90 degrees of are, of a pair of tubes moved in laterallyspaced relation between the two pairs of electrodes; first guide meansconstructed and arranged to feed a pair of metal tubes in predeterminedlaterally spaced relation to said two pairs of electrodes; second guidemeans constructed and arranged to guide an elongated metal strip towardsaid electrodes between said tubes; a pair of squeeze rolls engaging theouter surface of one of said tubes, each roll engaging said one tubeover the major portion of a quadrant of the surface thereof outwardly ofsaid electrodes; said rolls being mounted for rotation in planesdiverging outwardly of said one tube at substantially equal angles tothe common diametric plane of said tubes, and the peripheries of saidrolls at the outer surface of said one tube being spaced by an amount atleast equal to the thickness of said strip; squeeze roll means engagingthe outer surface of the other of said tubes, over substantially itscomplete semi-circumferential extent, laterally opposite said pair ofsqueeze rolls; said pair of squeeze rolls and said squeeze roll meansengaging the outer surfaces of said tubes as the tubes engage theelectrodes to press said tubes firmly against the opposite side edges ofsaid strip for flow of welding current from one electrode of each pairinto one tube, through the strip and through the other tube to the otherelectrode of the associated pair to simultaneously electric resistanceweld bothrtubes to opposite side edges of said strip; and transfer meansreceiving the joined tubes from said electrodes and constructed andarranged to return the joined tubes to a position in advance of saidguiding means but laterally offset, by the amount of such predeterminedlateral spacing, from the initial position for guiding of one joinedtube and an additional tube, in such predetermined laterally spacedrelation, to said two pairs of electrodes for electric resistance welduniting of another strip and said additional tube to said one joinedtube; the strip uniting the previously joined tubes passing between saidsqueeze rolls with the other previously joined tube passing outside saidpair of squeeze rolls.

4 Apparatus for forming a tubular component composed of laterally spacedrelatively elongated metal tubes integrally united by a longitudinalmetal web between adjacent tubes electric resistance welded along itsopposite side edges to the adjacent tubes; said apparatus comprising, incombination, a first pair of coaxial rotary electrodes mounted injuxtaposed electrically insulated relation and connected to oppositepolarity terminals of a source of Welding potential; a second pair ofcoaxial rotary electrodes mounted in juxtaposed electrically insulatedrelation and connected to opposite polarity terminals of a source ofwelding potential; said two pairs of electrodes being in verticallyadjacent relation, and correspondingly located electrodes of the twopairs being in substantial diametrical alignment vertically andlaterally and being at the same relative polarity; each electrode havinga curved tube engaging peripheral surface and the tube engaging surfacesof the electrodes of each pair diverging from each other in a directiontoward the electrode axis whereby the electrodes of one pair engage theupper inner quadrants throughout substantially 90 of arc, and theelectrodes of the other pair engage the lower inner quadrants throughoutsubstantially 90 of arc, of a pair of tubes moved in laterally spacedrelation between the two pairs of electrodes; first guide meansconstructed and arranged to feed a pair of metal tubes in predeterminedlaterally spaced relation to said two pairs of electrodes; second guidemeans constructed and arranged to guide an elongated metal strip towardsaid electrodes between said tubes; and squeeze roll means engaging theouter surfaces of said tubes as the tubes engage the electrodes to presssaid tubes firmly against the opposite side edges of said strip for flowof Welding current from one electrode of each pair into one tube,through the strip and through the other tube to the other electrode ofthe associated pair to simultaneously electric resistance weld bothtubes to opposite side edges of said strip, said squeeze roll meansincluding a pair of squeeze rolls engaging the outer surface of one ofsaid tubes; said rolls being mounted for rotation in planes divergingoutwardly of said one tube at substantially equal angles to the commondiametric plane of said tubes, and the peripheries of said rolls at theouter surface of said one tube being spaced by an amount at least equalto the thickness of said strip.

5. Apparatus for forming a tubular component composed of laterallyspaced relatively elongated metal tubes integrally united by alongitudinal metal web between adjacent tubes electric resistance weldedalong its opposite side edges to the adjacent tubes; said apparatuscomprising, in combination, a first pair of coaxial rotary electrodesmounted in juxtaposed electrically insulated relation and connected toopposite polarity terminals of a source of welding potential; a secondpair of coaxial rotary electrodes mounted in juxtaposed electricallyinsulated relation and connected to opposite polarity terminals of asource of welding potential; said two pairs of electrodes being invertically adjacent relation, and correspondingly located electrodes ofthe two pairs being in substantial diametrical alignment vertically andlaterally and being at the same relative polarity; each electrode havinga curved tube engaging peripheral surface and the tube engaging surfacesof the electrodes of each pair diverging from each other in a directiontoward the electrode axis whereby the electrodes of one pair engage theupper inner quadrants throughout substantially of arc, and theelectrodes of the other pair engage the lower inner quadrants throughoutsubstantially 90 of arc, of a pair of tubes moved in laterally spacedrelation between the two pairs of electrodes; first guide meansconstructed and arranged to feed a pair of metal tubes in predeterminedlaterally spaced relation to said two pairs of electrodes; second guidemeans constructed and arranged to guide an elongated metal strip towardsaid electrodes between said tubes; and squeeze roll means engaging theouter surfaces of said tubes as the tubes engage the electrodes to presssaid tubes firmly against the opposite side edges of said strip for flowof Welding current from one electrode of each pair into one tube,through the strip and through the other tube to the other electrode ofthe associated pair to simultaneously electric resistance weld bothtubes to opposite side edges of said strip, said squeeze roll meansincluding a pair of squeeze rolls engaging the outer surface of one ofsaid tubes, each roll engaging said one tube over the major portion of aquadrant of the surface thereof outwardly of said electrodes; said rollsbeing mounted for rotation in planes diverging outwardly of said onetube at substantially equal angles to the common diametric plane of saidtubes, and the peripheries of said rolls at the outer surface of saidone tube being spaced by an amount at least equal to the thickness ofsaid strip.

References Cited in the file of this patent UNITED STATES PATENTS1,521,857 Blum Jan. 6, 1925 1,542,984 Blum June 23, 1925 1,660,425Murray Feb. 28, 1928 1,844,407 Murray Feb. 9, 1932 2,381,742 Guirl Aug.7, 1945 2,537,503 Abbey Jan. 9, 1951 2,719,210 Chapman Sept. 27, 1955FOREIGN PATENTS 932,183 France Nov. 17, 1947

